15. Women of childbearing potential not using a medically approved means of contraception (i.e., oral or injectable contraceptives, intrauterine devices or diaphragm with spermicide, or transdermal hormonal patches). Abstinence will not be accepted as a medically approved means of contraception. Female patients will be considered to be of childbearing potential unless surgically sterilized by hysterectomy or bilateral tubal ligation, or post-menopausal for at least two years.